Spherical compass



Aug. 10, 1965 K. B. LEDGERWOOD SPHERICAL COMPASS 2 Sheets-Sheet 1 FiledJan. 23, 1962 Aug. 10, 1965 K. B. LEDGERWOOD SPHERICAL COMPASS 2Sheets-Sheet 2 Filed Jan. 23, 1962 United States Patent 3,199,210SPHERICAL COMPASS Kenneth B. Lcdgerwood, Dorchester, Mass, assignor toAll Hands, Incorporated, Hingham, Mass, at corporation of MassachusettsFiled Jan. 23, 1962, Ser. No. 168,151 4 Claims. (Cl. 33-223) Thisinvention relates to a spherical compass.

A spherical compass characteristically includes a compass card carriedin a liquid-filled enclosure with generally spherical inner surfaces.The whole point of the spherical inner surfaces is to avoid causingmovement in the liquid when the enclosure is moved by movement of theboat or other object carrying the compass, for liquid movement causesundesirable movement of the compass card, which is surrounded by theliquid. Nevertheless, much undesirable liquid movement has beencharacteristic of so-called spherical compasses heretofore available.Certain of this undesirable movement has been owing to the fact thatinner surfaces of enclosures were not in fact substantially spherical,containing on the contrary open relieved portions interrupting truespherical continuity .and providing in contact with the liquid enclosurepropelling surfaces at angles to tangents to what would constitute thespherical surface if uninterrupted and at even greater angles to theportions of spherical surface immediately adjacent to said relievedportions; these propelling surfaces acted on the portions of liquidadjacent them to drive such portions with the enclosure when the lattermoved, thus creating movement and turbulence within the overall body ofthe liquid. Other undesirable liquid movement has been owing .to thefact that expansion chambers have been provided outside the sphericalenclosure and communicating therewith through holes providing relievedportions as described; that movement of the boat or other mounting hasrepeatedly driven additional liquid by inertial effects through suchholes into such expansion chambers; that such expansion chambers havetypically been elastic, so that when such inertial effects were removedor modified they urged the liquid so moving back through such holes intothe spherical enclosure; and that in moving back through such holes,said liquid re-entered the spherical enclosure with a jet-effectdirectional flow either directly impinging on the compass card (inalmost all cases upsettingly non-centrally thereof) to undesirably moveit or causing turbulence in the main body of liquid wit-h similarultimate effect.

It is a primary object of the present invention to protect the compasscard against undesirable movement from both effects and tendencies abovementioned. It is a further object to provide an enclosure with aspherical inner surface free from open relieved portions providingliquidpropelling surfaces. A further object is to provide in saidenclosure 9. pivotally mounted indicating assembly which includes notonly the compass card and a magnet for driving it but also a compressionchamber, Other objects are to provide new and improved simple assemblyfeatures, to provide a novel construction additionally insulating theentire enclosure against shocks to and abrupt short-duration movementsof the boat or other mounting for the compass, and to provide forimproved fore-andaft pivotal mounting of the indicating assembly.

Other objects, features, and advantages will appear from the followingdescription of the presently preferred Bdhhilh Patented Aug, ill, 1965ice embodiment, taken together with the attached drawings thereof, inwhich:

FIG. 1 is a plan View of said presently preferred embod-intent;

FIG. 2 is a side elevational view, partially in section, thereof;

FIG. .3 is an isometric view on the enclosure for said embodiment,showing in dotted lines the indicator assembly contained therein;

FIG. 4 is a sectional view taken at 44 of FIG. 3;

FIG. 5 is a partial sectional view taken at 55 of FIG. 3;

*FIG. 6 is an exploded isometric view of a novel subcom-binationembodied in said preferred embodiment; and FIG. 7 is a sectional viewtaken at 7-7 of FIG. 4.

Referring now to the drawings in more detail, there is shown a moldedplastic skin .19 in which is seated a polyurethane foam cushion L2. Thefoam is soft and yieldable, like that used in furniture upholstering.For boat use the foam is desirably coated or of closed-cell character,to keep out water. The outer configuration of the foam cushion 12coincides with the inner configuration of the skin 10 where the twoelements are in contact. The inner con-figuration of the cushion 1.2 isspherical, to conform with the outer surface of the enclosure 1-6, wherethey are in contact. The upper portion of the enclosure '16 extends outthrough a hole in the upper portion of the cushion 12. The enclosure 16is formed of two transparent plastic hemispheres, joined by any suitablemeans, not shown, and is tilled with transparent liquid. Said hole inthe cushion 12 is of course smaller at its top than the diameter of thespherical enclosure, since said hole conforms to the surface of thespherical enclosure, and cooperates therewith along portions of thesurface of the latter well above its equator, indicated by 18. However,the foam cushion may easily be temporarily stretched to seat theenclosure 16 in the hole thereof. Extending all around said hole is areversely directed lip 20 defining with the main body of the cushion 12a groove in which is seated the mating edge of the skin 10, said edgedefining a circular but non-planar hole, as shown. The edge 22 of therigid skin It), assembled into the groove under the lip 2t after theenclosure 16 is in position, likewise detines a hole smaller than thediameter of said enclosure, and positively secures it againstdisplacement in use. The rigid plastic plate 24- secures the cushion 12against. downward displacement relative to the skin 1%.

The cushion 1 2 includes a hole 26 opening into zone 28 defined inwardlyby the enclosure 16. This hole and enclosure are to accept a small lightassembly (not shown) for illumination of the compass when needed, andplate 24 includes hole 30 for wires therefrom. Secured in the lowerhemisphere of enclosure 16 are a pair of flanged brass pins 3-2 on whichis pivot-ally mounted plastic gimbal ring 34. Pivotally mounted on brassflanged pins 36 inside gimba'l ring 34 is the indicator assembly,generally indicated at 38.

The pins 32 are portend-starboard of the compass and the pins 36 arefore-andaaft thereof. It has been found that .in modern higher-speedboat-s mounting the gimbals in this manner, rather than as in the priorart mounting the outer ring on fore-andcft ins, prov-ides for lesseneddisturbance of the compass by boat movement.

Adhesively secured to the lower hemisphere of enclosure 16 is plasticfiller boss 40 accepting filler screw 42, which extends through theenclosure 16, the end of the screw being aligned with the inner surfacethereof. A seal is provided by filler gasket 44.

The indicator assembly 38 includes a transparent plastic support member46 with a pair of upwardly extending mounting portions 48, an annulardownwardly extending support portion St the inner diameter of which isapproximately the same as the compass card diameter, and a transverselyextending central portion 52. Centrally of the portion 52 isforce-fittedly mounted a brass jewel shaft 54 carrying jewel 56;Supported on the jewel E6 is pivot pin 58, which isforce-fittedly heldin transparent plastic bushing so against movement relative'thereto. Thebushing 66 has abutment surfaces 62 which rest against the uppersurfaces of aluminum compass card as and a round shank portion 66 whichextends through a mating central hole in the compass card 64 andtherebeneath. The bushing 60 also includes, above, alongside, and belowthe compass card 64 a transversely extending slot 68 to facilitate aresilient gripping effect in the shank portion 66, upwardly throughwhich extends blind hole '70, and to accept the elongated ends of magnet'72. Adhesively secured to the lower surface of compass card 64 ismagnet 72, which has parallel fiat upper andlower surfaces, a pair ofopposed elongated end portions 74 and '76 the latter of which is pointedin a direction corresponding to the direction indicated as north onthecompass card thereabove, and an intermediate portion 78 between thesaid end portions with surfaces constituting portions of acylinder andmating with the inner surfaces of the slotted blind hole 70 through theshank portion 66 of the plastic bushing, which resiliently grip thecylindrical portions of the magnet to hold the latter and the compasscard (held between the magnet and the abutment surfaces 62 of thebushing) against movement relative to the pivot pin 58. The magnetincludes a countersunk central hole limiting upward movement of themagnet relative to the jewel shaft 54, which includes a frusto-conicalsurface cooperatingwith the similar surface counters unlc in the magnetto provide a stop.

Also mounted in support member 46 are lubbers line pins 8i Adhesivelysecured to the lower surface of support por tion 56) therearound is theflange 32 of upper compression chamber member 84'. Adhesively secured tothe flange $2 therebeneath is flange 86 of lower compression chambermember 88. The two expansion chamber members are formed from thintransparent cellulose acetate plastic sheet about .008 inch thick,include undulations 9i) and 92 for increased flexibility, and definetherebetween a sealed air pocket or compressible gas filled compressionchamber 94 having a depth less than half its diameter, for improved.stability. Extending through the support portions50 are a pair of holes95 which permit liquid communication with the top of upper compressionchamber member 84. l

Secured beneath compression chamber 9d is strap 36 carrying weight 98selected to tend to stabilize the indicating assembly 38 with thecompass card 64- in horizontal position without unduly increasing theweight of the indicating assembly relative to the weight of acorrespondingflvolume of the liquid with which the enclosure 16 isfilled.

For use, the enclosure 16 may be filled with liquids of ber will expandto increase the volumether'eof, on the: other hand, inthe event ofshrinkage in the volume of liquid present.

, No open relieved portions interrupt spherical continuity in theimproved compass of the present invention, to provide undesirable liquidpropelling surfaces upon euclosure movement. No holes to externalexpansion chambers through which jets of liquid may surge to undesirablyimpinge on the compass card and agitate the liquid are present.Furthermore, prevention of undesired disturbance of the compass card isfurther cooperatively promoted both by the novel gimballing arrangementinside of the enclosure and by the novel manner in which the enclosureis itself mounted for protection against shocks caused by short durationforces on the boat or other object carrying the compass. Transparency ofthe upper enclosure hemisphere permits reading the compass, andtransparency adjacent the Zone 255 permits lighting up the compass, asfor night use. The form and relationship of the elements taught,including the bushing-magnet-card subassembly permits easy andtrouble-free construction at considerably lowered assembly expense.

Other embodiments of my invention within the scope of the followingclaims will occur to those skilled in the art.

I claim:

1. A compass comprising a spherical enclosure at least part of which istransparent, transparent liquid disposed in said enclosure; a pivotallymounted support member inside said enclosure, a magnet-carrying compasscard pivotally carried by said support member thereabove, and a sealedgas-filled compression chamber carried by said support member below saidcompass card, said compass including a soft, yieldable foam membercupping. and carrying said enclosure and a rigid skin .mernber aroundsaid foam member, said skin member including a hole-defining edge seatedin a groove of said foam member, said foam member including a hole withtherearound a reversely directed lip defining with the main body ofsaidfoam membersaid groove, and less than half of said enclosureprotruding upwardly through said foam member hole, the latter being ofdiameter less than the outer diameter of said enclosure, whereby saidenclosure is insulated against shocks and compass card stability isimproved.

2. The compass of claim 1 in which the inner spherical surface definingsaid spherical enclosure is free from open relieved portions withliquid-propelling surfaces.

3. A. com-pass comprising a spherical enclosure at least part of whichis transparent, a body of transparent liquid enclosed by said enclosure,a support member pivotally mounted in said enclosure and contactinglysurrounded by said body, a magnet-carrying compass card pivotallymounted in saidsupport member and contactingly surrounded by said body,and a gas-filled compression cham ber carried by said support member,said chamber being surrounded by said body and'holding said gas out ofcontact with said'liquid, whereby an efiect on undesirable impingementsof currents within said body, on said compass card is produced resultingin great stability.

:iinproved compass card stability is achieved, said compass includingan:upwardly-extending jeweled shaft rigidly carried by said supp ortmember, a compass card pivot pin supported thereby, and an: assemblybushing rigidly carrying said compass card pivot pin, saidmagnet being'positioned beneath the compass card and provided with a pair ofelongated ends and a central generally cylindrical portion, said compasscard including a central hole therethrough, and said bushing including adownwardly extending slotted annular shank, abutment surfaces adjacent.said shank engaging the upper surface of said compass card andl'saidshank extending through s'aid'central hole of said compass card,gripping said.

cylindrical portion of said magnet, and accepting said elongated endsthrough the slotted portion, said magnet and said jeweled shaftcooperating to permit limited upward movement of said magnet relative tosaid jeweled shaft, whereby said pivot pin, bushing, compass card, andmagnet are held in rigid unitary relationship for desired movementrelative to said jeweled shaft and said support member carrying thesame.

References Cited by the Examiner UNITED STATES PATENTS 16,845 3/57 Kline33-225 1,980,415 11/34 Lumm 33223 ROBERT E.

FOREIGN PATENTS 1/44 France.

9/ 17 Germany.

6/ 39 Germany.

6/ 39 Great Britain.

HULL, Primary Examiner.

1. A COMPASS COMPRISING A SPHERICAL ENCLOSURE AT LEAST PART OFF WHICH ISTRANSPARENT, TRANSPARENT LIQUID DISPOSED IN SAID ENCLOSURE, A PIVOTALLYMOUNTED SUPPORT MEMBER INSIDE SAID ENCLOSURE, A MAGNET-CARRYING COMPASSCARD PIVOTALLY CARRIED BY SAID SUPPORT MEMBER THEREABOVE, AND A SEALEDGAS-FILLED COMPRESSION CHAMBER CARRIED BY SAID SUPPORT MEMBER BELOW SAIDCOMPASS CARD, SAID COMPASS INCLUDING A SOFT, YIELDABLE FOAM MEMBERCUPPING AND CARRYING SAID ENCLOSURE AND A RIGID SKIN MEMBER AROUND SAIDFOAM MEMBER, SAID SKIN MEMBER INCLUDING A HOLE-DEFINING EDGE SEATED IN AGROOVE OF SAID FOAM MEMBER, SAID FOAM MEMBER INCLUDING A HOLE WITHTHEREAROUND A REVERSELY DIRECTED LIP DEFINING WITH THE MAIN BODY OF SAIDFOAM MEMBER SAID GROOVE, AND LESS THAN HALF OF SAID ENCLOSURE PROTRUDINGUPWARDLY THROUGH SAID FOAM MEMBER HOLD, THE LATTER BEING OF DIAMETERLESS THAN THE OUTER DIAMETER OF SAID ENCLOSURE, WHEREBY SAID ENCLOSUREIS INSULATED AGAINST SHOCKS AND COMPASS CARD STABILITY IS IMPROVED.